574 THE PHYSIOLOGY OF REPRODUCTION 



uterine segment) upon the surrounding nerve ganglia. Supposing 

 this conclusion to be correct as applied to the bat, it is not quite 

 clear that it is equally appUcable to the human female and to other 

 animals. 



(5) Simpson 1 and others were of opinion that the "pains" of 

 labour were the indirect result of a partial separation of foetus and 

 decidua, brought about by the fatty degeneration of the latter in 

 the last stages of pregnancy, so that the foetus became virtually 

 converted into a foreign body, which caused the uterus to respond 

 accordingly. It is true that part of the inaternal placenta undergoes 

 degenerative changes towards the end of pregnancy, but there is no 

 evidence that this by itself is sufficient to cause a separation of the 

 foetus from the uterine, wall. 



(6) There is no evidence in support of the theory that the 

 exciting cause of parturition is an accumulation of carbon dioxide 

 in the blood, beyond the fact demonstrated by Brown-S^quard,^ 

 Keiffer,^ and others, that uterine contractions can be induced 

 experimentally by this means. 



(7) Spiegelberg* put forward the theory that parturition was 

 brought about through the action of isubstances secreted by the 

 fcjstus and passed into the maternal blood. These hypothetical 

 substances, which appear to have been comparable to Starling's 

 hormones, were supposed to act on the uterine centre in the spinal 

 cord. Spiegelberg suggested, further, that the exciting substances 

 were elaborated as a result of an insufficiency of nutrition, and were 

 an indication that the mature foetus required other sustenance than 

 that supphed to it through the placenta. This theory appears to be 

 devoid of all experimental basis, but it is not opposed by any of the 

 known facts.'' 



(8) Tyler Smith,* Minot,^ Beard,* and others have held the view 



that there is a connection between parturition and menstruatibn, the 



two processes being physiologically homologous. According to this 



theory, there is an increased tendency towards uterine contractions 

 • 



' Simpson, loc. cit. 



^ Brown-S6quard, EioperimentaZ Resea/rches, English translation, London, 

 1853. 



'' Keiffer, loc. cit. 



* Spiegelberg, " Die Dauer der Geburt," Lehrhuch der GehwtshvZfe, vol. ii., 

 1891. 



* Van der Heide states that he induced labour pains at full term in 

 pregnant women by injecting foetal blood-serum. According to the same 

 author the materhal blood of rats in late pregnancy contains substances toxic 

 to non-pregnant animals {Jmir. Med. Research, vol. ixix., 1914). 



° Tyler Smith, Partvjrition avd the Prinoiples and Practice of Obstetrics, 

 London, 1849. 



' Minot, " Uterus and Embryo,'' Jovr. of Morph., vol. ii., 1889. "Human 

 Embryology." 



' Beard, The Span of Gestation and the Cause of Birth, Jena, 1897. 



